图像时域滤波（二）

1.灰度变换

% 载入图像

fileurl = fullfile(pwd, 'images', 'IM1.dcm');

X = dicomread(fileurl);

X = im2uint8(mat2gray(X));
% 拷贝副本

Y1 = X;

Y1(X < 0.2*255) = 0.2*255;

Y1(X > 0.8*255) = 0.8*255;
% 二值化

Y2 = im2bw(X);
% log处理

Y3 = log(double(X));

% 直方图均衡化

Y4 = histeq(X);
% 显示

figure; imshow(X, []); title('原图');

figure; imshow(Y1, []); title('灰度压缩');

figure; imshow(Y2); title('二值化');

figure; imshow(Y3, []); title('非线性log');

figure; imshow(Y4, []); title('直方图均衡化');

2.直方图统计

I = imread('rice.png');
% 矩形框

rect = [10 10 20 20];
% 图像裁剪

J = imcrop(I, rect);
% 默认的直方图统计

[counts, x] = imhist(J);

figure;

subplot(2, 2, 1); imshow(I, []); title('原图像');

rectangle('Position', rect, 'EdgeColor', 'r');

subplot(2, 2, 2); imshow(J, []); title('裁剪图像');

subplot(2, 2, 3); imhist(I); axis auto; title('原图像直方图')

subplot(2, 2, 4); imhist(J); axis auto; title('裁剪图像直方图');

figure;

subplot(2, 2, 1); imshow(I, []); title('原图像');

rectangle('Position', rect, 'EdgeColor', 'r');

subplot(2, 2, 2); imshow(J, []); title('裁剪图像');

subplot(2, 2, 3); imhist(J); axis auto; title('默认的裁剪直方图');

subplot(2, 2, 4); plot(x, counts); axis auto;

set(gca, 'YLim', [0 30])

title('频数统计的直方图');

3.平滑滤波

clc; clear all; close all; 

I = imread('rice.png');

figure; imshow(I); title('原图像')

I = double(I);

h = [1 1 1

    1 1 1

    1 1 1]/9;

J = imfilter(I, h, 'replicate');

figure; imshow(mat2gray(J)); title('均值滤波');

S = medfilt2(I);

figure; imshow(mat2gray(S)); title('中值滤波');

4.锐化滤波

clc; clear all; close all; 

I = imread('rice.png');

figure; imshow(I); title('原图像');

I = double(I);

h = [1 2 1

    0 0 0

    -1 -2 -1];

J = imfilter(I, h, 'replicate');

figure; imshow(mat2gray(J)); title('sobel滤波器');

h2 = [0.1667 0.6667 0.1667

    0.6667 -3.3333 0.6667

    0.1667 0.6667 0.1667];

S = imfilter(I, h2, 'replicate');

figure; imshow(mat2gray(S)); title('拉普拉斯滤波器');

5.混合图像增强

clc; clear all; close all; 
% 加载图像
J = imread(fullfile(pwd, 'images', 'ct.tif'));
if ndims(J) == 3
    J = rgb2gra增强y(J);

end
% double变换

I = im2double(J);
% 拉普拉斯变换得到M1

h1 = fspecial('laplacian');

M1 = imfilter(I,h1);
% 与原图相加得到M2,锐化原图

M2 = M1+I;

% sobel

h2 = fspecial('sobel')';

h3 = fspecial('sobel');

Sx = imfilter(I, h2);

Sy = imfilter(I, h3);
% 梯度

M3 = sqrt(Sx.^2 + Sy.^2);
% 均值

h4 = fspecial('average');

M4 = imfilter(I,h4);

M5 = M2.*M4;

M6 = I+M5;
% 灰度拉伸

M7 = 2*M6.^1.15;

figure; 

subplot(241);imshow(I);title('原图像');

subplot(242);imshow(M1);title('拉普拉斯变换');

subplot(243);imshow(M2);title('锐化结果1');

subplot(244);imshow(M3);title('梯度');

subplot(245);imshow(M4);title('均值');

subplot(246);imshow(M5);title('锐化结果2');

subplot(247);imshow(M6);title('锐化增强');

subplot(248);imshow(M7);title('灰度拉伸');

res = M7;

figure; imshow(I); title('原图像');

figure; imshow(res); title('混合增强的效果');